Obviously there's no guarantee, and there's also the fact that we may not have every case documented, but if it is true that we have 0 case documented, that's pretty far from 600. Even if it's not "impossible", then at the very least it's less likely.

It's a simple binomial probability calculation. The probability of one or more blind schizophrenic people born in the US, assuming they're independent variables, is 1-0,999998^330000000. I don't have a calculator on hand that can calculate that, but it's more than 1 - 10^-87. So the odds that there is no link between the two is close to the odds of guessing a specific bitcoin wallet's key in one try.